1. Field
Exemplary embodiments of the present invention relate to an organic light emitting device and a method of fabricating the same.
2. Description of the Related Art
Out of flat panel display devices, an organic light emitting device is a self-emissive type device for emitting light due to an electrical excitation of an organic compound. Because the organic light emitting device does not need a backlight unit used in a liquid crystal display, it can be fabricated to be thin and light through a simple fabrication process. The organic light emitting device can be fabricated in low temperature environment. Furthermore, the organic light emitting device has various characteristics such as rapid response time, low power consumption, a wide viewing angle, and high contrast.
The organic light emitting device includes an organic emissive layer between an anode electrode and a cathode electrode. The organic light emitting device forms an exciton, which is a hole-electron pair, by combining holes received from the anode electrode and electrons received from the cathode electrode inside the organic emissive layer, and emits light by energy generated when the exciton returns to a ground level.
The organic light emitting device includes a plurality of pixels including red, green and blue organic emissive layers so as to achieve full color representation. The red, green and blue organic emissive layers can be patterned through a vacuum deposition method.
FIG. 1 is a cross-sectional view of a related art organic light emitting device.
As illustrated in FIG. 1, a thin film transistor T is positioned on a substrate 100. The thin film transistor T includes a semiconductor layer 105, a first insulating layer 110 that is a gate insulating layer, a gate electrode 115, a second insulating layer 120 that is an interlayer insulating layer, a source electrode 125a, and a drain electrode 125b. 
A third insulating layer 130 may be positioned on the thin film transistor T for planarization or passivation. An organic light emitting diode including a first electrode 140, an organic emissive layer 170, and a second electrode 180 is positioned in the third insulating layer 130.
The first electrode 140 is formed in each pixel, and electrically connected to the drain electrode 125b through the third insulating layer 130. A fourth insulating layer 150 including an opening 155 may be positioned on the first electrode 140. The opening 155 provides an electrical insulation between the first electrodes 140, and exposes a portion of the first electrode 140. The organic emissive layer 170 is positioned inside the opening 155. The organic emissive layer 170 may include red, green and blue organic emissive layers, and may be patterned in each pixel through a vacuum deposition method using a shadow mask. The second electrode 180 is positioned on the substrate 100 including the organic emissive layer 170, and formed in the form of a front electrode.
An organic light emitting device may be classified into a bottom emissive type device, a top emissive type device, and a dual emissive type device based on a traveling direction of light produced by an organic light emitting diode. Because light travels in an opposite direction to a substrate in a top emissive type organic light emitting device, a second electrode is formed of a transparent conductive film such as indium-tin-oxide (ITO) or a thin metal film so as to transmit light.
However, when the second electrode of the top emissive type organic light emitting device is formed as illustrated in FIG. 1, a surface resistance of the second electrode increases. Furthermore, because the second electrode is formed in the form of a common electrode in FIG. 1, signals transmitted to each pixel are delayed by the increased surface resistance of the second electrode. This results in non-uniformity of a luminance of each pixel. In particular, the delay of signals transmitted to each pixel increases in a large-sized organic light emitting device, and thus, it is difficult to display a desired image.